How to UNwarp wood in cold weather

I am immensely frustrated. I know how UNwarp wood when the weather is warm and sunny. However, it is bloody cold in northern Virginia and I really do not want to wait for spring (unless that is the only solution).

I have a collection of 1/4, and 3/8 stock that I wish to use in a project. Unfortunately it is all cupped and/or warped.

Any suggestions on corrective methods would be appreciated.

Many thanks,

Phil Stevens

11 replies so far

I don’t have a solution for cupped stock, except maybe to joint it. But it sounds like you are at or near your final thickness. But for warped and even twisted boards, I like to use heat (not steam, just heat). My favorite tool for this is a propane powered infra red paint stripper I bought many years ago. But I have never seen another one like it, and was not able to find a website for the company. Next up is the heat gun, which will work well, except you have to be careful not to scorch the wood. Clamp one end of the board in a vise or to a table or vertical post. Play the heat over the wood where the warp is until it is very hot (but not scorching). That should be on the inside of the warp. Now start gradually bending the wood to straighten it. I do this by eye. You’ll need to over bend. Take away the heat, and hold the board in this position for a couple of minutes. This will let it cool enough that it will now hold the new shape. If it isn’t right yet, repeat. If you went to far, you’ll have to reheat it to unbend it.

If the wood has a twist, you can clamp a handle onto the end to give you leverage to correct that. Maybe somebody else can help with the cupping.

I have a feeling a lot of wood that LJs feel obliged to joint could be treated this way. And by the way, this works very well for bending plywood, especially thinner panels.

I needed a 10’ oak crown molding for my kitchen. The only one I could find in town was badly warped. Resembled a ski. I got it at a discount (nobody else wanted it), and using the above method, was able to straighten it out easily. Total time was maybe 10 minutes.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

The warping has relieved stress in the wood. By unwarping it, you may well be introducing stress back into the wood, even with the use of heat. Unless you counteract that, it will likely just go back to its initial state.

I don’t know a lot about cold, being in texas, But often moisture is the key to warping, and winters get drier than usual. Is the problem related to the climate in your shop?? Also how would you un warp it in summer, that can’t be done in the winter? I ask that question honestly from the perspective of someone who suffered through a 75 degree day today. For me it is usually bringing the moisture back in line to relax the wood. So I am unsure what about your shop, or set up is allowing you to do it in the summer, but not the winter. While writing this scissors has offered an interesting solution, close to what I was thinking. I have done similar but with moisture, by ironing over top of a damp cotton rag on the cup side, and heat only on the crown side(with an industrial soldering iron I use for soldering door pans, not a home iron) With thin woods drying causes the shape changes In my experience. I am looking for an article I read. I kept a poster out of this at my office to remind me how things will change. Here is the next best thing I found. I will post the graphic next time I am at the office if you are interest pm me.

Monte Great insight, however in my experience “reaction wood” (I have also call it wyld or live) generally changes shape after physically processes, like jointing, ripping, or shaping. Wood that has changed shape while sitting in the shop is usually due to losing or gaining moisture. IMO the situation hillsboro is describing is from sitting. Although as mentioned in my first post, I don’t have a real read on how tensed or compressed wood acts in extreme temp change.

If the cupping matches the picture according to grain, you may be able to fix it by bringing moisture back in line, or with one of the other options mentioned here.

I wood agree that if it has done it once it will want to go that way again.

not necessarily, but that’s why it’s important to stack wood properly when drying it or when storing it long term. And yes there are some slices of wood that will cup, however most wood unless specified is going to be straight sawn instead of quarter sawn, which is what your diagram is pretty much showing. Quarter sawing produces better looking wood, but produces less lumber, so lumber mills tend to not do it as often and charge more for quarter sawn.

-- The mark of a good carpenter is not how few mistakes he makes, but rather how well he fixes them.

My thanks to all for the thoughts/comments. In answer to Joey’s question about fixing cupped lumber in warm weather: put it cupped side down on the grass early in the morning. The suns heat, and the wet grass will solve the problem. Just be sure to check the lumber often or you might end up with cupping in the opposite direction.

Clearly this is not an option in the winter. Virginia in the winter is cold and with the cold it is very dry in the house regardless of where one is. Therefore, despite how one stacks lumber problems arise.

I have discovered that careful use of a heat gun will solve the problem for my thin stock.

I understand now why It would help if it was summertime, not to brag, ok maybe a little, I could have used that method yesterday, as it was 80 degrees, but is basically the same as the ironing over a damp rag. Glad you are able to un cup things.